Microglial cells are defense of the central nervous system and they have many important tasks. Microglia cells are being activated and they migrate during the inflammation process which also releases inflammatory mediators. Celastrol, chinese medical herb has been used successfully for centuries in the treatment of various diseases because it has a strong therapeutic effect on autoimmune and inflammatory diseases. The aim of this study was to investigate the effect of celastrol on BV-2 microglial cells which were exposed to hypoxia in a period of 6 hours. We looked for morphological changes of microglial cells, their number, and the expression of the marker COX-2. By decrease of the number of microglial cells and by the change in their morphology we see toxic effects of celastrol and hypoxia. Reduced expression of COX-2 indicator of inflammation leads to the conclusion that celastrol has anti-inflammatory activity.